By the development of semiconductor devices and their peripheral technologies, imaging devices have been increased in functionality and reduced in size. One of applications of imaging devices is a photocopier. A conventional and widespread photocopier takes an image of a subject placed on platen glass of the photocopier. When a photocopier with such a structure takes an image of a thick book, a gutter of a page is significantly curved and cannot be in close contact with platen glass; thus, an image of the gutter is distorted or cannot be taken in some cases. Moreover, a book itself might be damaged. The invention disclosed in Patent Document 1 solves such a problem by making platen glass have a generally V-shaped cross section.